1. Field of the Invention
The invention relates to disk brakes and, more particularly, relates to a self-sealing, self-contained electromagnetic disk brake. The invention additionally relates to a method of assembling a self-sealing, self-contained electromagnetic disk brake.
2. Discussion of the Related Art
Electromagnetic disk brakes are widely used in a variety of applications such as dynamic brakes for motor input shafts and/or output shafts and as static or "park-and-hold" brakes for motors and the like. A typical electromagnetic disk brake of this type includes a friction disk that is coupled with the shaft so as to be movable axially relative to the shaft but to be rotationally fixed relative to the shaft. In static braking applications, the brake is applied by compressing the friction disk between a stationary reaction plate and an axially-movable clapper plate to provide the desired holding action, and the brake is released by energizing the electromagnet to retract the clapper plate to allow the friction disk to rotate freely. In dynamic braking applications, the brake is applied while the shaft is rotating, either by energizing an electromagnetic actuator to overcome the force of a return spring or by de-energizing a normally-energized actuator to permit a compression spring to apply the brake.
Whether used in static braking applications or dynamic braking applications, the traditional electromagnetic disk brake exhibits characteristics increasing its cost and decreasing its versatility. For instance, it is usually necessary to encase the moving components of the brake in a separate cover to protect them from dust and other foreign matter. Covers suitable for these purposes usually are attached to the brake's field cup and/or mounting plate, and/or to the motor or other structure serviced by the brake. The need for this separate cover increases the cost of brake components as well as the cost of labor required to fabricate and assemble the brake. It also increases the overall size of the brake.
The complexity of the typical electromagnetic disk brake is increased further by the need for stand-offs in the brake to set the brake's air gap. Elimination of these stand-offs would significantly facilitate assembly and reduce the cost of labor and materials.
In the case of a spring-applied, electromagnetically released brake, the complexity of the brake is increased still further by the brake's spring actuator arrangement, which consists of a plurality (typically three) of compression springs spaced evenly around the periphery of the brake and mounted in spaced apertures in the inner surface of the field cup. Considerable expense is involved in forming these apertures.
Spring-applied, electromagnetically-released brakes having a manual release or manual override feature exhibit still another problem. Specifically, in brakes of this type, a manual release lever can be selectively rotated to force the brake's clapper plate away from the friction disk(s). These release levers typically have significant rotational play when the brake is actuated, leading to rattling and possibly to false actuation of indicator switches which are intended to be closed only upon manual brake release. Prior anti-rattle mechanisms for this type of brake have ranged from complex at best to ineffective at worst.
Electromagnetic disk brakes designed specifically for use with electric motors exhibit still another disadvantage. Specifically, brakes of this type include a mounting plate for attaching the brake to the motor's endbell. This mounting plate necessarily increases the size and weight of the brake, limiting the brake's usefulness in some applications. Attachment of the brake to the motor endbell also requires modification of the existing endbell structure to accept the mounting plate. It also tends to be relatively labor intensive.
The need has therefore arisen to provide an electromagnetic disk brake that has a minimum number of parts to reduce cost and weight, that is easy to fabricate by the brake manufacturer, and that is easy to install by the brake purchaser.